Computing devices, such as notebook computers, personal data assistants (PDAs), mobile communication devices, and portable entertainment devices (such as handheld video game devices, multimedia players, and the like) have user interface devices, which are also known as human interface devices (HID), that facilitate interaction between the user and the computing device. One type of user-interface device that has become more common is a touch-sensor pad (also known as a “touchpad”). A touchpad replicates mouse X/Y movement by using two defined axes, which contain a collection of sensor elements that detect the position of a conductive object such as a finger. Mouse right/left button clicks can be replicated by two mechanical buttons, located in the vicinity of the touchpad, or by tapping commands on the touchpad itself. The touchpad provides a user-interface device for performing such functions as positioning a cursor and selecting an item on a display. These touch pads may include multi-dimensional sensor arrays for detecting movement in multiple axes. The sensor array may include a one-dimensional sensor array to detect movement in one axis. The sensor array may also be two-dimensional to detect movement in two axes.
One type of touchpad operates by way of capacitance sensing utilizing capacitive sensors. The capacitance detected by a capacitive sensor changes as a function of the proximity of a conductive object to the sensor. The conductive object can be, for example, a stylus or a user's finger. In a touch-sensor device, a change in capacitance detected by each sensor in the X and Y dimensions of the sensor array, due to the proximity or movement of a conductive object, can be measured by a variety of methods. Regardless of the method, usually an electrical signal representative of the capacitance detected by each capacitive sensor is processed by a processing device, which in turn develops electrical signals representative of the position of the conductive object in relation to the touch-sensor pad in the X and Y dimensions. A touch-sensor strip, slider, or button operates on the same capacitance-sensing principle.